Description
Part of the Professional Line (often associated with Woodward SEG or Woodward Protection Devices), this unit provides high-speed phase differential protection to isolate internal faults within the generator stator windings.
Commercial and Supply Chain Status
- Condition: New Original (Factory Sealed / New Surplus) or Refurbished (Tested to OEM Specifications)
- Warranty: 12-Month Industrial Warranty
- Availability: Limited availability; legacy protection module (Verify component lifecycle status with the supplier)
- Lead Time: Ships within 2 to 5 business days depending on localized stock and testing verification
- Pricing: Price subject to market availability and core scarcity; contact us for a firm quote.
Technical Specifications
| Parameter | Value |
| Product Line | SEG Professional Line / Woodward High Tech Line |
| Model Configuration | XD1-G11 (Generator Differential Protection) |
| Rated Frequency (f_n) | 50 Hz / 60 Hz (Configurable or specific hardware build) |
| Nominal Current Input (I_n) | 1 A or 5 A secondary inputs (Verify via exact sub-wiring code) |
| Auxiliary Supply Voltage | Dependent on sub-code (Typically wide-range e.g., 24 V DC or 110–230 V AC/DC; verify with nameplate) |
| Setting Range (Differential Current) | Adjustable percentage threshold (typically 10% to 50% of I_n) |
| Tripping Characteristic | Biased/restrained differential curve to prevent spill-current false trips |
| Output Contacts | Heavy-duty trip relay contacts, signaling/alarm contacts |
| Mounting Form Factor | Flush mounting into switchgear doors or 19-inch rack frames |
| Standard Compliance | IEC 60255, CE Mark |
Functional Architecture and Fault Protection Logic
The XD1-G11 relies on current balance comparison principles to monitor the health of generator phases. It requires matching current transformer (CT) sets positioned at both the neutral star-point side and the terminal output side of the generator stator windings.
Core Protection Mechanics
- Phase Differential Protection (87G): The module continuously computes the vector difference between incoming and outgoing currents for each individual phase. Under normal conditions or external through-faults, the current entering equals the current exiting (\sum I = 0). An internal insulation breakdown or phase-to-phase short within the winding breaks this balance, causing immediate, instantaneous tripping.
- Restraint (Bias) Curve: To counteract unequal CT saturation during high external through-fault currents, the XD1-G11 applies a stabilizing bias percentage curve. This prevents nuisance trips caused by transient CT calculation errors during external system faults.
Engineering Insights: Installation and Lifecycle Maintenance
Current Transformer (CT) Matching Constraints
⚠️ CRITICAL ENGINEERING REQUIREMENT: For the differential logic to perform safely and accurately, all CTs feeding the XD1-G11 must share identical transformation ratios, magnetic cores, and saturation classes (typically Class PX or 5P20 accuracy ratings). Disparities in CT behavior can cause false residual currents under heavy external loads, resulting in a spurious generator trip.
Commissioning Stability Test
Prior to commercial operation, execute a complete primary or secondary stability test:
- Inject test currents through the CT paths to simulate an external fault condition.
- Verify that the internal differential current reading remains near zero while the restraint/stabilizing current scales appropriately.
- Reverse the polarity of one CT set intentionally to verify that the unit identifies the simulated internal fault and initiates the trip sequence.
Legacy Lifecycle Warning
The XD1 series represents a mature, legacy protection line originally engineered under the SEG / Woodward brand portfolio. When managing critical generator protection architectures, maintain cold-spare modules on site or formulate a migration plan to current digital protection relays (such as the Woodward High Tech Line or MR series) to avoid extended downtime should an aging unit experience an internal power supply failure.
Frequently Asked Questions
Q: Can the XD1-G11 be used for transformer differential protection? A: No. The XD1-G is specifically biased and scaled for generator protection where there is no phase shift or voltage conversion ratio to compensate for between the two sets of CTs. For transformer applications, a dedicated transformer differential relay (such as an XD1-T or modern equivalent) must be utilized to handle vector group adaptations and inrush current filtering.
Q: How do I identify the specific auxiliary operating voltage for my XD1-G11 variant? A: Because the generic model number XD1-G11 may have factory modification codes appended or stamped on the side plate, always read the specific voltage and terminal mapping diagram printed on the physical device housing enclosure before connecting external control power.
Q: What steps should be taken if the “Fault” LED lights up continuously? A: An internal fault or self-test failure indicates a hardware problem inside the micro-controller or analog-to-digital converter circuitry. Disconnect power, check internal connection ribbon cables, and if the error persists on a subsequent cold start, replace the module immediately to prevent operating the generator without differential protection.
